1. Field of the Invention
The present invention relates to a device for concentrating and transforming radiant energy with a multistage energy flux transformation system. In particular, this invention relates to linear focus solar energy concentrators.
2. Description of Prior Art
It is well known that cylindrical parabolic mirrors and Fresnel lenses are used to concentrate the solar radiation which intensity is otherwise fairly low at the ground level for its direct use. While parabolic mirrors are notably superior in concentration over the lenses, this prior art design concept has the limitation of requiring tight shape and alignment tolerances to keep the concentrated sunlight focused onto a narrow target area. On the other hand, there is a limitation of energy collection ability of one-stage energy concentrators related to finite angle (one half degree) the sun subtends. As a result, the concentrated beam projected on the target has poorly defined boundaries because they are formed by the rays mainly emanated from the edge portions of the solar disk. These outer rays also have a longer path length giving rise to a larger transversal spread of the focal line.
Various arrangements have been proposed in the past for improving the sunlight collection of linear focus devices by introducing secondary optics into the concentrated beam reflected from the primary parabolic mirror. One of the major problems of such past proposals is the inherent problem of partial shadowing the primary concentrator by the secondary and relative inaccessibility of the focal line which hampers the utility of the devices.
The known multi-reflection systems, such as those derived from Cassegrain telescope optics, have a further drawback that the entire flux reflected by the primary mirror is entirely redirected back by the secondary mirror resulting in a longer path of concentrated flux and decreased concentration efficiency.
None of these previous efforts provides the benefits attendant with the present invention. The present invention achieves its intended purposes, objects and advantages over the prior art devices through a new, useful and unobvious combination of component elements and operation, at a reasonable cost to manufacture, and by employing only readily available materials.
It is an object of this invention to provide an improved radiant energy flux transformation system which increases the concentration of incident flux impinging on the primary reflector structure without disposing the secondary collector in the path of incident flux.
Another object of this invention is to provide an improved radiant energy flux transformation system which provides improved focusing for off-axis rays with minimum reflections and minimizes energy losses.
It is yet another object of the present invention to provide a system for radiant energy flux transformation which is composed by relatively simple optical elements and which is of compact and sturdy construction.
A further object is to provide an efficient reflective energy collecting system capable of substantially uniformly distributing the concentrated flux over a receiver surface.
Other objects and advantages of this invention will be apparent to those skilled in the art from the following disclosure and appended claims.